JP5180485B2 - Method for manufacturing fuel cell separator, fuel cell separator and fuel cell - Google Patents

Description

  The present invention relates to a method for producing a separator for a fuel cell made of Ti or Ti alloy for a polymer electrolyte fuel cell used for portable devices such as mobile phones and personal computers, household fuel cells, fuel cell vehicles, etc. The present invention relates to a battery separator and a fuel cell.

In recent years, fuel cells are expected as an energy source for solving global environmental problems and energy problems.
In particular, polymer electrolyte fuel cells can be operated at low temperatures, and can be reduced in size and weight, so they can be applied to household cogeneration systems, power supplies for portable devices, and fuel cell vehicles. It is being considered.

  Here, a general polymer electrolyte fuel cell has a catalyst layer serving as an anode and a cathode on both sides of a solid polymer membrane that is an electrolyte, a gas diffusion layer on the outer side, and a fuel gas flow on the outer side. The separator is provided with a path.

  This separator is required not only to function as a gas flow path but also to take out a current, and therefore has high conductivity. Conventionally, carbon separators have been used. However, because the thickness dimension has to be increased due to strength, it is difficult to say that it is preferable from the viewpoint of reducing the size and weight.

  In order to reduce the size and weight of the separator, it is considered that the separator is formed of a metal that can be thinned. However, since the inside of the fuel cell (solid polymer fuel cell) is in an acidic atmosphere, it can be said that the environment is easily corroded by metals. Therefore, a metal separator used in a fuel cell needs to have good corrosion resistance and conductivity.

  Also, metals such as stainless steel and Ti have good corrosion resistance by forming a passive film on the surface, but this passive film increases the contact resistance with the gas diffusion layer, so that the conductivity is improved. It is known to inhibit the power generation efficiency of the fuel cell.

  On the other hand, metals that do not form a passive film such as iron have good conductivity but are easily corroded and eluted, and the eluted ions deteriorate the catalytic properties and reduce the ionic conductivity of the solid polymer membrane. Therefore, it is known that the power generation characteristics of the fuel cell are deteriorated as a result.

For this reason, the surface of a metal separator is plated with gold (for example, see Patent Document 1), or the surface of a stainless steel or Ti separator is adhered to a surface of a noble metal or a noble metal alloy by ion deposition or plating ( For example, refer to Patent Document 2), and a structure in which a noble metal layer is formed on the surface of a separator made of a corrosion-resistant metal material (for example, refer to Patent Document 3) has been proposed.
These inventions attempt to maintain high corrosion resistance and low contact resistance by forming a noble metal having high corrosion resistance on a metal surface without forming a passive film on the surface.
JP-A-10-228914 JP 2001-6713 A JP 2004-158437 A

  However, the invention described in Patent Document 1 not only deteriorates the adhesion of gold unless the surface passive film is removed, but also increases the contact resistance due to this passive film (that is, the conductivity is low). Lower). Therefore, the passive film is removed by performing the surface activation process, but since the passive film is formed in the cleaning process performed before the plating process, there is a drawback that sufficient adhesion cannot be obtained. There is a disadvantage that the contact resistance cannot be lowered.

  Moreover, the invention described in Patent Document 2 performs a process of precipitating Pt as a noble metal by a corrosion reaction while mechanically polishing the surface of stainless steel or Ti. When such a treatment is performed, Pt is deposited on the portion where the passive film has been removed, so that the contact resistance decreases (that is, the conductivity increases), but the pinhole (where the substrate partially appears on the surface) In other words, stainless steel and Ti are eluted from the pinhole when used in an acidic atmosphere such as a fuel cell, and the power generation characteristics of the fuel cell deteriorate. There are drawbacks. In addition, although a method of blasting with glass beads plated with precious metal has been proposed, since the separator is required to have high dimensional accuracy, there is a drawback that it becomes difficult to use due to deformation that can occur by blasting. .

  In the invention described in Patent Document 3, since the noble metal layer is formed by plating, it is considered that the noble metal layer is formed on the passive film. For this reason, there are drawbacks that sufficient adhesion cannot be obtained and contact resistance cannot be lowered.

In addition to plating, there is a method of providing a high corrosion resistance by forming a noble metal film on a stainless steel or Ti substrate by a vapor deposition method such as sputtering, vacuum deposition, or ion plating.
In such a method, in order to improve the adhesion of the noble metal layer, the substrate is irradiated with an argon ion beam in a low gas pressure argon gas atmosphere before the noble metal layer is formed, or a negative bias is applied to the substrate. It is common to form a noble metal layer after removing dirt, a passive film, etc. on the surface of the substrate by generating argon plasma by applying it and causing argon ions to collide with the substrate. According to this method, since the passive film is removed, a sufficiently low contact resistance can be obtained. However, since it takes time to remove the passive film by such a method, there is a disadvantage that productivity is lowered.

  An object of the present invention is for a fuel cell capable of producing a separator for a fuel cell made of Ti or Ti alloy having excellent corrosion resistance, high adhesion of a noble metal layer, low contact resistance, and excellent productivity. To provide a separator manufacturing method, to provide a fuel cell separator manufactured thereby, and to a fuel cell using the fuel cell separator.

In order to solve the above-described problems, a method for manufacturing a separator for a fuel cell according to the present invention includes a recess forming step, a noble metal layer forming step, and a heat treatment step.
As described above, in the method for manufacturing a fuel cell separator according to the present invention, a gas flow path for allowing gas to flow through at least a part of the surface of the substrate as a fuel cell separator made of Ti or Ti alloy is formed by the recess forming step. And forming a recess for forming a noble metal layer, and the step of forming the noble metal layer includes at least one or more kinds of noble metals selected from Ru, Rh, Pd, Os, Ir, Pt and Au on the surface of the substrate on which the recess is formed. A noble metal layer having a thickness of 2 nm or more is formed by plasma CVD. Then, by heat-treating the substrate on which the noble metal layer is formed under a predetermined condition by the heat treatment step, the diffusion layer and / or the passive film in which the elements of the noble metal layer and the Ti of the substrate are mutually diffused are crystallized. Thus, it is possible to form a passive film having improved adhesion and conductivity with the noble metal layer. Adhesion with the noble metal layer can be obtained by enhancing the consistency between the crystal lattice of the noble metal and the crystallized passive film.
Therefore, the method for producing a separator for a fuel cell according to the present invention is excellent in corrosion resistance and high adhesion of the noble metal layer by performing a heat treatment step after the noble metal layer formation step by the plasma CVD method without performing a complicated step. A fuel cell separator having a low contact resistance can be easily produced with high productivity.
The predetermined heat treatment temperature in the heat treatment step is 300 to 800 ° C., and the predetermined oxygen partial pressure in the heat treatment step is at least one selected from Ru, Rh, Pd, Os, and Ir. In some cases, the pressure is 1.33 Pa or less, and in the case where the noble metal is at least one selected from Pt and Au, the oxygen partial pressure is equal to or less than atmospheric pressure.
In addition, the method for producing a separator for a fuel cell according to the present invention increases the conductivity of the passive film by restricting the heat treatment temperature to a specific range, or increases the conductivity of the passive film or between the noble metal layer and the substrate. The film can be removed, or Ti of the substrate exposed to the pinhole can be oxidized to produce titanium oxide. In addition, it is possible to diffuse the noble metal element and Ti mutually and appropriately.
Furthermore, the method for producing a separator for a fuel cell can easily and appropriately increase the conductivity of the passive film by appropriately changing the upper limit of the oxygen partial pressure in the heat treatment step according to the type of the noble metal used. The passive film between the layer and the substrate can be removed, and a noble metal layer can be formed on the substrate.

In the method of manufacturing a fuel cell separator according to the present invention, it is preferable that the noble metal layer forming step forms the noble metal layer by heating the substrate to 300 to 800 ° C.
The formation of the noble metal layer by the plasma CVD method can be performed at about 1000 ° C. or less. However, in the noble metal layer forming step in the method for manufacturing the fuel cell separator of the present invention, the noble metal layer is formed in the temperature range described above. Thus, the heat treatment process which is the next process can be performed as it is, that is, with the same apparatus and at the same temperature, so that the productivity can be further improved.

In order to solve the above-described problem, the fuel cell separator according to the present invention is a fuel made of Ti or Ti alloy in which a recess for forming a gas flow path through which gas flows is formed on at least a part of the surface. A noble metal layer having a thickness of 2 nm or more comprising at least one kind of noble metal selected from Ru, Rh, Pd, Os, Ir, Pt and Au is formed on the surface of the substrate as a battery separator by plasma CVD. The precious metal layer is formed and heat-treated at a predetermined heat treatment temperature and a predetermined oxygen partial pressure, the predetermined heat treatment temperature is 300 to 800 ° C., and the predetermined oxygen partial pressure is obtained. Is at least 1.33 Pa when the noble metal is at least one selected from Ru, Rh, Pd, Os and Ir, and the noble metal is selected from Pt and Au For at least one or more elements, is characterized in that an oxygen partial pressure under the atmospheric pressure.
As described above, in the fuel cell separator of the present invention, the noble metal layer is formed on the substrate at a relatively low temperature by the plasma CVD method, and further, the elements of the noble metal layer and the Ti of the substrate are formed by heat treatment. Mutually diffused diffusion layers can be formed. In addition, the conductivity of the passive film between the noble metal layer and the substrate can be increased, or the passive film can be removed.
In addition, since the fuel cell separator of the present invention is heat-treated with the heat treatment temperature limited to a specific range, the conductivity of the passive film between the noble metal layer and the substrate is enhanced, or the passive film Is removed, and Ti of the substrate exposed to the pinhole can be oxidized to produce titanium oxide. In addition, a diffusion layer in which a noble metal element and Ti are diffused appropriately and appropriately can be formed.
Furthermore, the separator for a fuel cell according to the present invention is thus more easily and adequately conductive in the passive film by appropriately changing the upper limit of the oxygen partial pressure during the heat treatment in accordance with the type of noble metal used. The passive film can be removed, and a noble metal layer can be formed on the substrate.

In the fuel cell separator according to the present invention, the noble metal layer is preferably formed by heating the substrate to 300 to 800 ° C.
As described above, the fuel cell separator according to the present invention forms the noble metal layer by heating the substrate in a specific temperature range. Therefore, it is more preferable that the elements of the noble metal layer and Ti of the substrate are diffused mutually. A layer can be formed. Moreover, the electroconductivity of the passive film between a noble metal layer and a board | substrate can be improved more, or a passive film can be removed more suitably.

The fuel cell separator according to the present invention is formed on the surface of a substrate as a fuel cell separator made of Ti or Ti alloy in which a recess for forming a gas flow path for allowing gas to flow through at least a part of the surface is formed. A noble metal layer containing at least one or more kinds of noble metals selected from Ru, Rh, Pd, Os, Ir, Pt and Au, and a titanium oxide layer having high conductivity (oxidation) between the noble metal layer and the substrate. It is preferable that at least one of a diffusion layer in which the element of the noble metal layer and Ti of the substrate diffuse to each other is formed.
As described above, the fuel cell separator according to the present invention has a noble metal layer containing a specific noble metal formed on the surface thereof, so that the contact resistance can be lowered, and a diffusion layer and / or a titanium oxide layer is formed. Therefore, the adhesion of the noble metal layer can be increased. In addition, since the above-described diffusion layer and / or the above-described titanium oxide layer is formed, the electrical resistance between the substrate and the noble metal layer can be prevented from becoming high, so that the contact resistance can be lowered.

  The fuel cell according to the present invention preferably uses the above-described fuel cell separator. Since the fuel cell of the present invention uses the above-described fuel cell separator, it has excellent corrosion resistance, high adhesion of the noble metal layer, low contact resistance, and excellent productivity.

The separator for a fuel cell according to the present invention is excellent in corrosion resistance, crystallizes the passive film or removes the passive film, so that the adhesion of the noble metal layer is high, the contact resistance is low, and the productivity is further improved. It is possible to manufacture a separator for a fuel cell made of Ti or Ti alloy which is excellent in the above.
Moreover, the fuel cell separator according to the present invention has excellent corrosion resistance, high adhesion of the noble metal layer, low contact resistance, and excellent productivity.
The fuel cell according to the present invention has excellent corrosion resistance, high adhesion of the noble metal layer, low contact resistance, and excellent productivity.

Next, the best mode for carrying out the method for manufacturing a fuel cell separator, the fuel cell separator and the fuel cell according to the present invention will be described with reference to the drawings as appropriate. In the drawings to be referred to, FIG. 1 is a flowchart for explaining the steps of the method for manufacturing a fuel cell separator according to the present invention. FIGS. 2A and 2B are cross-sectional views of a fuel cell separator according to the present invention. FIG. 3 is an explanatory diagram for explaining a method of measuring contact resistance. FIG. 4 is a diagram showing an example of the shape of the gas flow path formed on the surface of the substrate. FIG. 5 is a diagram showing a state in which a part of a fuel cell using the fuel cell separator of the present invention is developed.
In the drawings to be referred to, reference numeral S1 denotes a recess forming process, reference numeral S2 denotes a noble metal layer forming process, reference numeral S3 denotes a heat treatment process, reference numeral 1 denotes a fuel cell separator, reference numeral 2 Indicates a substrate, reference numeral 3 indicates a noble metal layer, reference numeral 4 indicates a diffusion layer, reference numeral 10 indicates a single cell, reference numeral 11 indicates a gas flow path, and reference numeral 12 indicates a gas diffusion layer. Reference numeral 13 denotes a solid polymer membrane, and reference numeral 20 denotes a fuel cell.

First, the manufacturing method of the separator for fuel cells of this invention is demonstrated.
As shown in FIG. 1, the manufacturing method of the fuel cell separator 1 of the present invention includes a recess forming step S1, a noble metal layer forming step S2, and a heat treatment step S3.

The recess forming step S1 is a gas flow path 11 for circulating a gas such as hydrogen gas or air over at least a part of the surface of the substrate 2 as a fuel cell separator made of Ti or Ti alloy (see FIGS. 4 and 5). A recess for forming the is formed. Here, the surface of the substrate 2 refers to a surface that forms the outside of the substrate 2, and includes a so-called front surface, back surface, and side surface.
Here, the apparatus for forming the gas flow path on at least a part of the surface of the substrate 2 is not particularly limited, and a conventionally known apparatus capable of achieving a predetermined purpose can be appropriately used. .
Prior to the formation step S1, it is preferable to form the substrate 2 in a predetermined size or shape, such as a vertical width, a horizontal width, and a thickness.

  The noble metal layer forming step S2 is selected from Ru, Rh, Pd, Os, Ir, Pt and Au on the surface of the substrate 2 made of Ti or Ti alloy having the recesses (the entire surface of the substrate 2 or a part of the surface). The noble metal layer 3 having a thickness of 2 nm or more and containing at least one kind of noble metal is formed by plasma CVD (plasma chemical vapor deposition).

  Examples of the substrate 2 include 1 to 4 types of pure Ti substrates stipulated in JIS H 4600, and substrates of Ti alloys such as Ti—Al, Ti—Ta, Ti-6Al-4V, and Ti—Pd. Can do. However, the substrate 2 that can be used in the present invention is not limited to these, and even Ti alloys containing other metal elements can be suitably used.

  Noble metals such as Ru, Rh, Pd, Os, Ir, Pt and Au are excellent in corrosion resistance even though they do not form a passive film, and are excellent in conductivity because they are transition metals. It is known that these noble metal elements have properties similar to each other. Therefore, by forming the noble metal layer 3 containing a noble metal appropriately selected from these, it is possible to have good corrosion resistance and conductivity.

The thickness of the noble metal layer 3 formed in the noble metal layer forming step S2 needs to be 2 nm or more. When the thickness of the noble metal layer 3 is less than 2 nm, an excessively large number of pinholes are formed. Therefore, when heat treatment described later is performed, oxidation of Ti or Ti alloy reaches below the noble metal layer 3. The contact resistance cannot be lowered. The thickness of the noble metal layer 3 formed in the noble metal layer forming step S2 is more preferably 3 nm or more, and most preferably 5 nm or more.
The upper limit value of the thickness of the noble metal layer 3 is not particularly limited, but is preferably 500 nm or less from the viewpoint of reducing the time and cost required for forming the noble metal layer 3.

  In the noble metal layer forming step S2, the above-described noble metal noble metal layer 3 is formed by plasma CVD. In the plasma CVD method, since the noble metal layer 3 can be formed on the substrate 2 even at a relatively low temperature from room temperature to several hundred degrees Celsius, not only can damage to the substrate 2 (for example, warpage or strength reduction) be reduced. Since the noble metal layer 3 of noble metal can be formed in a relatively wide area, productivity is improved.

In the noble metal layer forming step S2, it is preferable to form the noble metal layer 3 by heating the substrate 2 to 300 to 800 ° C. Since it can transfer to heat treatment process S3 mentioned later quickly, manufacture of separator 1 for fuel cells can be made easy.
In performing the noble metal layer forming step S2, the substrate 2 can be cleaned in advance using an organic solvent such as acetone. Such cleaning is preferable because pinhole formation and poor adhesion due to contamination on the surface of the substrate 2 can be reduced.

  Next, in the heat treatment step S3, the substrate 2 on which the noble metal layer 3 is formed in the noble metal layer forming step S2 is heat-treated at a predetermined heat treatment temperature and a predetermined oxygen partial pressure to form the noble metal layer 3, and the noble metal layer 3 and the substrate 2, a diffusion layer 4 in which elements of the noble metal layer 3 and Ti of the substrate 2 are mutually diffused, and a highly conductive crystallized passive film (a titanium oxide layer 5 (see FIG. 2B)). )) Is formed to produce a fuel cell separator 1.

That is, in the heat treatment step S3, a passive film (titanium oxide) partially or wholly crystallized is formed by heat treatment under predetermined conditions, or the elements of the noble metal layer 3 and Ti of the substrate 2 are mutually bonded. The diffusion layer 4 can be formed by diffusing.
Here, a part or all of the passive film formed on the surface of the substrate 2 before the heat treatment is crystallized by the heat treatment. During the crystallization, the passive film immediately below the noble metal layer 3 is thinned by diffusion of oxygen into the Ti base material because the supply of oxygen is blocked by the noble metal layer 3, and the oxygen oxide-deficient titanium oxide. It changes to (titanium oxide having an oxygen-deficient gradient structure). This crystallized titanium oxide becomes an n-type semiconductor whose conductivity is increased when oxygen is deficient than the stoichiometric ratio. That is, the conductivity of the passive film formed on the surface of the substrate 2 by heat treatment can be improved. Examples of such a crystal structure of titanium oxide include a rutile type crystal and a brookite type crystal. Note that the rutile-type crystal means a crystal having the same crystal structure as a rutile crystal, the brookite-type crystal means a crystal having the same crystal structure as Burukkai preparative crystal. The oxide film 4 having such an oxygen-deficient rutile crystal and brookite crystal is more easily obtained by performing a heat treatment with a lower oxygen partial pressure, such as a portion covered with the noble metal layer 3. It is even easier to obtain heat treatment under conditions with less oxygen.

  Further, by continuing the heat treatment or increasing the heat treatment temperature, the passive film before the heat treatment and the layer of titanium oxide having high conductivity formed as described above disappear, and the noble metal layer 3 and A diffusion layer 4 in which a noble metal element and Ti are mutually diffused is formed between the substrates 2.

When such a heat treatment is performed, even if the passive film remains, dirt such as hydrocarbon existing on the passive film is decomposed by heat and diffused into the noble metal layer 3. It is considered that the noble metal layer 3 comes into contact with the surface of the clean passive film and / or the crystallized passive film (that is, oxygen-deficient titanium oxide) as well as a clean surface. It is considered that the consistency between the passivated film and the crystal lattice of the noble metal is improved, and the adhesion is improved.
Further, when the heat treatment is performed at a high temperature or for a long time, the passive film disappears completely, and a diffusion layer 4 in which elements of the noble metal layer 3 and Ti of the substrate 2 are diffused is present between the noble metal layer 3 and the substrate 2. It is formed.

  Therefore, the method for producing a separator for a fuel cell of the present invention is not necessary when the passive film remains only by performing the heat treatment step S3 after the noble metal layer formation step S2 by the plasma CVD method without performing complicated steps. A part or all of the dynamic film can be a crystallized passive film (titanium oxide layer 5) having oxygen-deficient conductivity, and if no passive film remains, the noble metal layer Since the diffusion layer 4 of the element 3 and Ti of the substrate 2 can be formed, the fuel cell separator 1 having high adhesion to noble metal and low contact resistance can be easily produced with high productivity.

The heat treatment temperature in the heat treatment step S3 is preferably 300 to 800 ° C. In order to increase the adhesion of the noble metal layer 3 and reduce the contact resistance, the passive film is crystallized, the passive film is removed, or Ti exposed to the pinholes is oxidized to ensure the corrosion resistance of the separator. This is to make it happen.
If the heat treatment temperature is less than 300 ° C., it takes time to crystallize the passive film and remove the passive film, which is not practical. In addition, the noble metal element and Ti of the substrate 2 may not sufficiently diffuse to each other.
Further, when the heat treatment temperature exceeds 800 ° C., the diffusion is too fast, so that the noble metal element and the Ti of the substrate 2 diffuse too much, and titanium diffuses to the outermost surface of the noble metal layer 3 and oxygen in the heat treatment atmosphere. As a result, a titanium oxide layer (oxide film) containing a rutile crystal and a brookite crystal may be formed. However, since such an oxide film is formed in contact with an oxygen-containing atmosphere, it becomes an oxide film with insufficient oxygen deficiency and has higher corrosion resistance than the passive film (titanium oxide layer 5), but the contact resistance. Is unfavorable because of the high. The heat treatment temperature is more preferably 350 to 750 ° C, and most preferably 380 to 730 ° C. Even in such a temperature range, if heat treatment is performed for a long time, titanium may diffuse to the surface and an oxide film may be formed. Therefore, it is preferable to appropriately adjust the heat treatment time with respect to the heat treatment temperature.

The heat treatment time in the heat treatment step S3 depends on the heat treatment temperature, but the passive film existing between the noble metal layer 3 and the substrate 2 is crystallized to reduce the contact resistance (that is, improve the conductivity) or passivate. In order to remove or sufficiently thin the film, it is preferably 1 to 60 minutes, more preferably 5 to 50 minutes.
If the heat treatment time is less than 1 minute, the conductivity of the passive film may not be improved and the passive film may not be removed sufficiently. For this reason, not only the adhesion of the noble metal layer 3 cannot be increased, but also the contact resistance cannot be decreased.
On the other hand, if the heat treatment time exceeds 60 minutes, although depending on the heat treatment temperature and the thickness of the noble metal layer 3, the noble metal element and Ti of the substrate 2 may diffuse excessively to form an oxide film on the outermost surface. It becomes easy to be done. As described above, the formation of an oxide film is not preferable because the contact resistance tends to increase. Further, although depending on the temperature of the heat treatment, the noble metal element and Ti of the substrate 2 may diffuse too much.

The oxygen partial pressure in the heat treatment step S3 is preferably set as appropriate depending on the type of noble metal used. Among the noble metals mentioned above, Pd, Ru, Rh, Os, and Ir are oxidized and the contact resistance is increased when the oxygen partial pressure is high.
In the present invention, the oxygen partial pressure is the pressure occupied by oxygen in the heat treatment furnace in which the heat treatment step S3 is performed (in the present invention, the composition of the atmosphere is that nitrogen: oxygen is approximately 4: 1). ).

Specifically, when the noble metal is at least one selected from Ru, Rh, Pd, Os, and Ir, the oxygen partial pressure should be 1.33 Pa (1 × 10 ⁻² Torr) or less. preferable.
If the oxygen partial pressure in the heat treatment step S3 exceeds 1.33 Pa (1 × 10 ⁻² Torr), since there is too much oxygen in the atmosphere for the heat treatment, these noble metals are likely to be oxidized and the contact resistance tends to be high. . The oxygen partial pressure is preferably as low as possible, more preferably 0.665 Pa (5 × 10 ⁻³ Torr or less), and still more preferably 0.133 Pa (1 × 10 ⁻³ Torr or less).

Even under low oxygen partial pressure conditions, Ti exposed to pinholes and the like is oxidized as long as oxygen is present in the atmosphere. However, since the oxidation of Ti does not proceed excessively under low oxygen partial pressure conditions, even if there is a portion where the noble metal layer 3 is not formed on the substrate 2, an appropriate oxide film is formed in the portion. Will be.
That is, even if it is used in an acidic atmosphere, the portion where the noble metal layer 3 is formed has good conductivity, and the noble metal layer 3 has good corrosion resistance, such as pinholes. In this case, the titanium oxide layer 5 (see FIG. 2B) is formed at the place where the noble metal layer 3 is not formed, so that the corrosion resistance is not deteriorated.
The heat treatment of the substrate 2 on which the noble metal layer 3 is formed by the plasma CVD method can be performed by using a conventionally known heat treatment furnace such as an electric furnace or a gas furnace capable of reducing the pressure in the furnace.

On the other hand, since Au and Pt are not oxidized, they can be heat-treated in an air atmosphere. Therefore, when the noble metal is at least one selected from Pt and Au, the oxygen partial pressure can be made equal to or lower than the oxygen partial pressure at atmospheric pressure.
As described above, when the noble metal layer forming step S2 is performed at 300 to 800 ° C., after the plasma CVD method is finished, the supply of the source gas is stopped and the heat treatment is performed in a low oxygen atmosphere chamber. Since step S3 can be performed, the manufacture of the fuel cell separator 1 can be facilitated, which is preferable.
Here, the source gas means a gasification of a noble metal for which the noble metal layer 3 is to be formed. For example, when forming the noble metal layer 3 of Pd, palladium chloride is heated to, for example, 300 ° C. and evaporated. And can be used as a raw material gas.

Here, a normal product using Ti as a base material has an amorphous passive film formed on the surface thereof, and Ti in the base material is bonded to hydrogen by the passive film. It is known to prevent embrittlement. Therefore, for example, under the use conditions of about 25 ° C. and about 0.1 MPa (1 atm), the above-described passive film prevents hydrogen from being absorbed, thereby preventing Ti and hydrogen in the base material from being combined. This makes it difficult to become brittle.
However, when exposed to hydrogen at high temperature and high pressure (eg, 80 to 120 ° C., 0.2 to 0.3 MPa) like a separator for a fuel cell, the above-described passive film is amorphous. Therefore, it is difficult to sufficiently prevent hydrogen absorption, and Ti in the base material may be combined with the absorbed hydrogen to be embrittled. Even when the noble metal layer 3 is formed on the substrate 2 by the plasma CVD method, there is a portion where the substrate 2 such as a pinhole is exposed on the surface, so that hydrogen is absorbed from the pinhole and the substrate 2 There is a possibility that the substrate 2 becomes brittle by bonding with Ti in the base material.

On the other hand, in the present invention, by performing heat treatment at 300 to 800 ° C. in the heat treatment step S3, Ti between the noble metal layer 3 and the substrate 2 and Ti of the substrate 2 exposed in the pinhole are oxidized, A titanium oxide layer 5 (see FIG. 2B) including at least one of a rutile type crystal and a brookite type crystal is formed. Such a titanium oxide layer 5 has an effect of blocking hydrogen absorption (simply referred to as “hydrogen absorption blocking effect”) higher than that of an amorphous passive film. Therefore, the titanium oxide layer 5 is exposed to hydrogen under high temperature and high pressure as described above. Even in such a case, Ti of the substrate 2 does not bond with hydrogen and the substrate 2 is not easily embrittled. In addition, although the above-mentioned hydrogen absorption inhibition effect can be obtained by heat treatment under a high oxygen partial pressure such as atmospheric pressure conditions, among the above-mentioned noble metals, Pd, Ru, Rh, Os, and Ir are oxygen partial pressures. If it is high, an oxide film is formed. Therefore, in order to combine the above-described hydrogen absorption preventing effect and conductivity, the oxygen partial pressure in the heat treatment step S3 of the present invention is set to 1.33 Pa (1 × 10 ⁻² Torr). It is preferable that In the case of a noble metal such as Au or Pt that is not oxidized, even if the heat treatment step S3 is performed under atmospheric pressure conditions, it is possible to have both a hydrogen absorption preventing effect and conductivity.

As mentioned above, although one Embodiment of the manufacturing method of the separator for fuel cells which concerns on this invention was described, even if it is embodiment described below, it can implement suitably.
For example, a noble metal layer 3 having a thickness of 2 nm or more comprising at least one kind of noble metal selected from Ru, Rh, Pd, Os, Ir, Pt and Au on the surface of a substrate 2 made of Ti or Ti alloy. A step of forming a gas flow path for circulating a gas by, for example, pressing or the like on at least a part of the surface of the substrate 2 on which the noble metal layer 3 is formed. A method of manufacturing a fuel cell separator can include a recess forming step to be formed and a heat treatment step in which the substrate 2 on which the recess is formed is heat-treated at a predetermined heat treatment temperature and a predetermined oxygen partial pressure.

  Further, for example, a noble metal having a thickness of 2 nm or more comprising at least one kind of noble metal selected from Ru, Rh, Pd, Os, Ir, Pt and Au on the surface of the substrate 2 made of Ti or Ti alloy. A noble metal layer forming step for forming the layer 3 by plasma CVD, a heat treatment step for heat-treating the substrate 2 on which the noble metal layer 3 is formed at a predetermined heat treatment temperature and a predetermined oxygen partial pressure, and the surface of the heat-treated substrate 2 A method of manufacturing a separator for a fuel cell, which includes a recess forming step for forming a recess for forming a gas flow path through which gas is circulated, for example, by pressing or the like at least in part.

Next, the fuel cell separator 1 according to the present invention manufactured by the method for manufacturing a fuel cell separator of the present invention will be described in detail with reference to FIG.
As shown in FIG. 2 (a), the fuel cell separator 1 according to the present invention is provided with a recess for forming a gas flow path 11 (see FIG. 4) through which gas flows at least at a part of the surface. A noble metal layer 3 containing at least one kind of noble metal selected from Ru, Rh, Pd, Os, Ir, Pt and Au is formed on the surface of a substrate 2 made of Ti or Ti alloy. .
More specifically, the fuel cell separator 1 according to the present invention includes at least one or more kinds of noble metals selected from Ru, Rh, Pd, Os, Ir, Pt and Au on the surface of the substrate 2. A noble metal layer 3 having a thickness of 2 nm or more is formed by plasma CVD, and the noble metal layer 3 is heat-treated at a predetermined heat treatment temperature and a predetermined oxygen partial pressure to form the noble metal layer 3, A diffusion layer 4 in which elements of the noble metal layer 3 and Ti of the substrate 2 are mutually diffused is formed between the substrates 2.
The significance of setting the thickness of the noble metal layer 3 in the above range, using the plasma CVD method, and defining the heat treatment temperature and oxygen partial pressure of the heat treatment has already been described in detail, and the description thereof is omitted. To do.

The thickness of the noble metal layer 3 formed on the substrate 2 is preferably 1.5 nm or more.
If the thickness of the noble metal layer 3 is less than 1.5 nm, the barrier effect of the noble metal layer 3 becomes insufficient, and a passive film is formed in the portion immediately below the diffusion layer 4 of the noble metal layer 3 and the substrate 2, resulting in contact resistance. May grow.
In addition, although there is no upper limit of the thickness of the noble metal layer 3, it is preferable that it is 500 nm or less from a viewpoint of cost.

The diffusion layer 4 prevents the electrical resistance (contact resistance) between the substrate 2 and the noble metal layer 3 from increasing.
A suitable thickness of the diffusion layer 4 is 1 nm or more. If the thickness of the diffusion layer 4 is within these ranges, the above-described effects can be suitably achieved.
The thickness of the diffusion layer 4 can be realized by performing heat treatment under appropriate conditions. It is preferable that the heat treatment under appropriate conditions is determined by an appropriate experiment or the like according to the type of noble metal used within the range of the above heat treatment temperature and heat treatment time.

  Further, when the fuel cell separator 1 according to the present invention includes the titanium oxide layer 41, for example, as shown in FIG. 2B, it is selected from Ru, Rh, Pd, Os, Ir, Pt, and Au. The titanium oxide layer 5 is formed between the noble metal layer 3 containing at least one kind of noble metal and the substrate 2 (that is, the base material). In addition, when the pinhole P etc. are formed in the noble metal layer 3, and the part which the board | substrate 2 exposed to the surface exists, the titanium oxide layer 5 can also be formed directly under the said pinhole P. FIG. In the present invention, it is preferable to form the titanium oxide layer 5 between the noble metal layer 3 and the substrate 2 and at least one of the portions where the substrate 2 is exposed on the surface (pinhole P). More preferred.

  If the titanium oxide layer 5 has a thickness of about 0.5 to 10 nm, it can have both a hydrogen absorption preventing effect and conductivity. Since the titanium oxide layer 5 is covered with the noble metal layer 3 or formed under a low oxygen partial pressure, the titanium oxide layer 5 contains at least one of a rutile type crystal and a brookite type crystal more than a normal passive film. obtain.

Next, the fuel cell according to the present invention will be described with reference to the drawings as appropriate.
As shown in FIG. 5, the fuel cell 20 according to the present invention is manufactured using the above-described fuel cell separator 1 according to the present invention, and can be manufactured as follows.
For example, a predetermined number of substrates 2 made of Ti or Ti alloy is prepared, and the predetermined number of substrates 2 is set to a predetermined size of 95.2 mm in length × 95.2 mm in width × 19 mm in thickness, and For example, a recess having a groove width of 0.6 mm and a groove depth of 0.5 mm is formed in the center portion of the surface by machining or etching to form a gas flow path 11 having a shape as shown in FIG.

  Then, the substrate 2 having the recesses is ultrasonically cleaned with an organic solvent such as acetone, and then set in a chamber in which the plasma CVD method is performed. Then, the inside of the chamber is evacuated, and after introducing argon gas, RF (high frequency) is applied to the substrate 2 to excite the argon gas and generate plasma. Next, palladium chloride as an evaporation source is heated, and evaporated palladium chloride gas is supplied to form the noble metal layer 3 on the substrate 2. The substrate 2 on which the noble metal layer 3 is formed in this manner is put in a heat treatment furnace, pulled to a predetermined degree of vacuum, and then subjected to a heat treatment that is heated at 500 ° C. for 5 minutes to produce a predetermined number of fuel cell separators 1.

  Note that productivity can be improved by preparing a large number of substrates 2 in advance and collectively forming the noble metal layer 3 and performing heat treatment. In addition, according to the present invention, it is not necessary to physically remove the passive film with an argon ion beam or the like before forming the noble metal layer 3 as in a conventionally known method. improves. In particular, in the case of Au or Pt, it is not necessary to draw a vacuum, and heat treatment can be performed with an oxygen partial pressure at atmospheric pressure, so that productivity can be further improved.

  Next, as shown in FIG. 5, for example, two fuel cell separators 1 that are manufactured in a predetermined number are disposed so that the surfaces on which the gas flow paths 11 are formed face each other, and the gas flow paths 11 are formed. A gas diffusion layer 12 such as carbon cloth C for uniformly diffusing the gas on the film is disposed on each surface, and a platinum catalyst is placed on the surface between one gas diffusion layer 12 and the other gas diffusion layer 12. The single cell 10 is produced with the solid polymer film 13 applied therebetween. Similarly, by stacking a plurality of single cells 10 produced into a cell stack (not shown), and attaching and connecting other parts necessary for the fuel cell, it has good corrosion resistance and conductivity. The fuel cell (solid polymer fuel cell) 20 according to the present invention can be produced.

  The solid polymer membrane 13 used in the fuel cell 20 can be used without particular limitation as long as it has a function of moving protons generated at the cathode electrode to the anode electrode. A fluorine-based polymer film having a group can be preferably used.

  The fuel cell 20 thus manufactured introduces fuel gas (for example, hydrogen gas with a purity of 99.999%) into the fuel cell separator 1 arranged as an anode electrode through the gas flow path 11. Air is introduced into the fuel cell separator 1 arranged as the cathode electrode through the gas flow path 11. At this time, the fuel cell 20 is preferably heated and kept at about 80 ° C., and the dew point temperature is preferably adjusted to 80 ° C. by passing the hydrogen gas and air through the heated water. The fuel gas (hydrogen gas) and air may be introduced at a pressure of 2026 hPa (2 atm), for example.

The fuel cell 20 is uniformly supplied to the solid polymer film 13 by the gas diffusion layer 12 by introducing hydrogen gas into the anode electrode in this way, and the solid polymer film 13 uses the following formula (1). Reaction occurs.
H ₂ → 2H ⁺ + 2e ⁻ (1)
On the other hand, the fuel cell 20 is uniformly supplied to the solid polymer film 13 by the gas diffusion layer 12 by introducing air into the cathode electrode, and the reaction of the following formula (2) is performed in the solid polymer film 13. Arise.
4H ⁺ + O ₂ + 4e ⁻ → H ₂ O (2)
As described above, the reaction of the above formulas (1) and (2) occurs in the solid polymer film 13, so that a voltage of about 1.2V is theoretically obtained.

  Here, as described above, since the fuel cell 20 according to the present invention uses the fuel cell separator 1 according to the present invention in which at least the noble metal layer 3 is formed, the fuel using the conventional metal separator is used. It becomes possible to have good corrosion resistance and conductivity as compared with the battery.

Next, the fuel cell separator manufacturing method, fuel cell separator, and fuel cell of the present invention will be described in detail by comparing an example that satisfies the requirements of the present invention with a comparative example that does not satisfy the requirements of the present invention. To do.
<Example A>
A Ti substrate (width 2 cm × 5 cm, thickness 1 mm) made of one kind of pure Ti as defined in JIS H 4600 is ultrasonically cleaned with acetone, and then applied to an electrode in a chamber for performing plasma CVD. It was attached and the inside of the chamber was evacuated to a vacuum of 0.00133 Pa (1 × 10 ⁻⁵ Torr) or less.
Argon gas was introduced into the chamber and the pressure was adjusted to 26.6 Pa (0.2 Torr). Thereafter, RF (high frequency) was applied to the substrate electrode to excite the argon gas to generate argon plasma. Thereafter, palladium chloride is heated to 300 ° C. to evaporate to form a raw material gas, which is introduced into the chamber to form a 2 nm thick Pd noble metal layer (hereinafter referred to as “noble metal layer (Pd)”). Formed. Further, the titanium substrate was turned over, and a noble metal layer (Pd) having a thickness of 2 nm was formed on the back surface of the substrate by the same method.
In the same manner as described above, a substrate in which the thickness of the noble metal layer (Pd) of Pd was 1 nm, 3 nm, 5 nm, and 10 nm was produced.

Next, these substrates on which the noble metal layer is formed are put into a heat treatment furnace, the inside of the furnace is evacuated to 0.133 Pa (1 × 10 ⁻³ Torr), and heat treatment is performed by heating at 500 ° C. for 15 minutes. The inside was cooled, and when the temperature reached 100 ° C., a test plate (corresponding to a fuel cell separator) on which a noble metal layer (Pd) was formed was taken out.
In addition, it was set as the test plates 1-5 in an order from thickness with a thin noble metal layer (Pd) formed (in order of thickness 1, 2, 3, 5, 10 nm).

(1) About these test plates 1-5, the contact resistance before and behind heat processing was measured with the load 98N (10 kgf) using the contact resistance measuring apparatus 30 shown in FIG. That is, for each of the test plates 1 to 5, both surfaces thereof are sandwiched by carbon cloth C and C, and the outside is pressurized with 98 N using copper electrodes 31 and 31 having a contact area of 1 cm ² , and a direct current power source 32 is used. Then, 7.4 mA electricity was applied, the voltage applied between the carbon cloths C and C was measured with the voltmeter 33, and the contact resistance was calculated.
(2) Further, each of the test plates 1 to 5 was immersed in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, and then contact resistance was measured again in the same manner as described above. In addition, after the heat treatment of (1) and the contact resistance of (2), 12 mΩ · cm ² or less was accepted.
(3) Moreover, the adhesion test of the noble metal layer (Pd) before and after the heat treatment was evaluated by a cross-cut tape peeling test. The cross-cut tape peel test was performed in accordance with the method described in the plating adhesion test method defined in JIS H8504.
Table 1 shows the results of (1) contact resistance before and after heat treatment, (2) contact resistance after being immersed in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, and (3) cross-cut tape peeling test.

From the results shown in Table 1, it can be seen that the contact resistance of any of the test plates 1 to 5 is reduced by performing the heat treatment.
In particular, the test plates 2 to 5 having a noble metal layer (Pd) thickness of 2 nm or more have a very small contact resistance after heat treatment of 5.3 mΩ · cm ² or less, and are excellent in conductivity. all right. It was also found that even after immersing in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, the contact resistance does not increase greatly and has high corrosion resistance. Moreover, as a result of the cross-cut tape peeling test conducted after the heat treatment, it was found that there was no peeling and that the adhesion between the noble metal layer and the substrate was high (all examples).

  On the other hand, the test plate 1 having a thickness of 1 nm of the noble metal layer (Pd) shows that the cross-cut tape peeling test performed after the heat treatment shows no peeling and high adhesion between the noble metal layer and the substrate. It was found that the contact resistance after a 1000-hour immersion in an aqueous sulfuric acid solution (pH 2) at 80 ° C. was greatly increased (Comparative Example).

  When the cross section of the test plate 4 (noble metal layer (Pd) thickness 5 nm) was observed with a TEM (transmission electron microscope), an oxide (that is, a passive film) was observed between the noble metal layer and the substrate. Instead, a diffusion layer in which Ti and Pd diffused to each other was observed with a thickness of about 5 nm.

<Example B>
In the same manner as in Example A, a noble metal layer of noble metals (Au and Pt) was formed to a thickness of 10 nm on two substrates made of Ti-6Al-4V alloy by plasma CVD. In addition, as source gas at this time, the thing which heated and evaporated gold chloride and platinum chloride at 300 degreeC was used.
Thereafter, the Ti-6Al-4V alloy plate on which the noble metal layer is formed is placed in a heat treatment furnace, and the inside of the furnace is evacuated to 0.00133 Pa (1 × 10 ⁻⁵ Torr), and then the furnace is heated to 500 ° C. A substrate (test plate) on which a precious metal layer (Au) was formed by heating and introducing dry air, adjusting the pressure in the furnace to 0.00665 Pa (5 × 10 ⁻⁵ Torr) and performing heat treatment for 1 minute 6) A substrate (test plate 7) on which a noble metal layer (Pt) was formed was produced.

(1) The contact resistance of these test plates 6 and 7 before and after heat treatment was measured. The contact resistance was measured in accordance with <Example A>, but the carbon cloth C, C was changed to an Au foil (not shown), and the voltage applied between the Au foils was measured. The contact resistance was calculated.
In addition, (2) The contact resistance after 1000 hours of immersion in an 80 ° C. sulfuric acid aqueous solution (pH 2) is measured, and (3) the adhesion test of the noble metal layer (Au) and the noble metal layer (Pt) before and after the heat treatment. Evaluation was made by a cross-cut tape peeling test. In addition, after the heat treatment of (1) and the contact resistance of (2), 0.5 mΩ · cm ² or less was accepted.
Further, in order to examine the interface structure between the noble metal thin film and the Ti-6Al-4V substrate, the cross section of the test plate 6 was observed with a transmission electron microscope (TEM). The TEM observation conditions were a sample thickness of about 100 nm, an acceleration voltage of 200 kV, and a magnification of 1.5 million times.

  Table 2 shows the results of (1) contact resistance before and after heat treatment, (2) contact resistance after being immersed in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, and (3) cross-cut tape peeling test.

  From the results shown in Table 2, it was found that the test plates 6 and 7 had lower contact resistance and improved adhesion due to heat treatment under oxygen partial pressure conditions at atmospheric pressure. Furthermore, even after being immersed in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, no increase in contact resistance was observed, indicating that the corrosion resistance was also excellent. Moreover, from the result of observation by TEM, it was confirmed that there was a titanium oxide layer having a thickness of about 5 nm between the noble metal layer (Au) and the substrate. Furthermore, when the crystal structure of the titanium oxide layer was examined by electron diffraction (nano-diffraction) performed with the beam diameter reduced to about 1 nm, it was found that rutile crystals were included.

<Example C>
Various noble metals shown in Table 3 were formed in a thickness of 5 nm on a Ti-5Ta substrate by plasma CVD in the same manner as in <Example A>.
Thereafter, the substrate on which the noble metal layer is formed is put in a heat treatment furnace, evacuated to 0.00133 Pa (1 × 10 ⁻⁵ Torr), heated to the heat treatment temperature shown in Table 3, and then the oxygen content shown in Table 3 is obtained. Oxygen was introduced while evacuating the furnace so that the pressure was increased, and heat treatment was performed for the heat treatment time shown in Table 3 to produce test plates 8 to 17.

Using these test plates 8 to 17, (1) contact resistance before and after heat treatment was measured. The contact resistance was measured according to <Example A>. In <Example C>, measurement was performed using a carbon cloth.
(2) Further, after each of the test plates 8 to 17 was immersed in an aqueous sulfuric acid solution (pH 2) at 80 ° C. for 1000 hours, the contact resistance was measured again in the same manner as described above. In addition, after the heat treatment of (1) and the contact resistance of (2), 12 mΩ · cm ² or less was accepted.
Table 3 shows the results of (1) contact resistance before and after heat treatment, and (2) contact resistance after being immersed in an 80 ° C. sulfuric acid aqueous solution (pH 2) for 1000 hours.

From the results shown in Table 3, among the test plates 8 to 14 in which the oxygen partial pressure was 1.33 Pa (1 × 10 ⁻² Torr) or less and heat treatment was performed at 300 to 800 ° C., the test plates 8 to 13 were It has been found that low contact resistance can be obtained.

On the other hand, since the processing time of the test plate 14 was too long, the diffusion layer of Pd and Ti grew too much, and Ti diffused to the outermost surface and titanium oxide was formed on the outermost surface. It did not drop.
The test plate 15 had a high oxygen partial pressure, so Pd was oxidized and the contact resistance did not decrease.
Since the heat treatment temperature of the test plate 16 was high, the diffusion layer of Au and Ti grew too much, and Ti diffused to the outermost surface and titanium oxide was formed on the outermost surface, so the contact resistance did not decrease. .
Since the test plate 17 had a low heat treatment temperature, the passive film could not be crystallized, and the thickness was hardly changed. Therefore, the contact resistance was hardly decreased and the contact resistance after immersion in sulfuric acid was low. Further, circular peeling with a diameter of about 1 mm was observed.

<Example D>
In the same manner as in Example A, a substrate made of Ti-5Ta alloy was heated to 500 ° C. by plasma CVD, and a noble metal layer (Pd) was formed thereon with a thickness of 5 nm. Thereafter, the source gas is stopped and the plasma excitation is stopped. Exhaust is performed while introducing dry air so that the pressure in the chamber becomes 0.00133 Pa (1 × 10 ⁻⁵ Torr). The test plate 18 was manufactured by maintaining the temperature at 5 ° C. for 5 minutes to produce the test plate 18, and then the chamber heater was turned off, and the substrate was cooled to 100 ° C. in the chamber and taken out.
When the contact resistance after heat treatment was measured by the same method as in Example A, it was 3.7 mΩ · cm ² , and it was found that low contact resistance was obtained.

<Example E>
First, eight Ti substrates (width 2 cm × 5 cm, thickness 0.2 mm) made of one kind of pure Ti specified in JIS H 4600 were prepared. By performing plasma CVD under the same conditions as described in <Example A> on the surfaces of these Ti substrates, Au and Pt noble metal layers were formed with a thickness of 10 nm on the respective Ti substrates (test). Plates 18-25). In addition, as the source gas used in the plasma CVD method, a gas obtained by evaporating gold chloride and platinum chloride by heating at 300 ° C. was used (the type of source gas used at this time is “noble metal” in Table 4 below). ("In" or "Pt").
Thereafter, the test plates 19 and 23 on which the noble metal layer was formed were heat-treated at 500 ° C. for 1 minute under atmospheric pressure conditions (oxygen partial pressure 2.13 × 10 ⁴ Pa).

Further, the test plates 20, 21, 24, and 25 on which the noble metal layer is formed are placed in a vacuum heat treatment furnace, the pressure in the furnace is evacuated to 0.00133 Pa (1 × 10 ⁻⁵ Torr), and then heated to 500 ° C. As shown in Table 4 below, the oxygen partial pressure in the furnace is 0.133 Pa (1 × 10 ⁻³ Torr) or 0.00133 Pa (1 × 10 ⁻⁵ Torr) by introducing dry air. The heat treatment was performed under such an oxygen partial pressure, with a heat treatment temperature of 500 ° C. and a heat treatment time of 5 minutes.
In addition, for comparison with the test plates 19 to 21 and 23 to 25, the two Ti substrates of the test plates 18 and 22 were subjected to the heat treatment shown in Table 4 after forming a noble metal layer of Au and Pt with a thickness of 10 nm. No heat treatment was performed under the conditions.

The contact resistances of the test plates 18 to 25 described above were measured and calculated under the same conditions as described in <Example B>.
Further, these test plates 18 to 25 are put in a gas phase part of a sealed container containing water and 0.3 MPa (3 atm) of hydrogen, and heated at 120 ° C., so that the humidity becomes about 100%. After exposure for 500 hours in a humidified pure hydrogen (purity 99.99%) atmosphere (hereinafter simply referred to as “humidified pure hydrogen atmosphere”), it is placed in a graphite crucible in an inert gas (Ar) stream. The sample is heated and melted together with tin by the graphite resistance heating method, hydrogen is extracted together with other gases, the extracted gas is passed through a separation column to separate hydrogen from other gases, and the separated hydrogen is detected for thermal conductivity. The hydrogen concentration (ppm) in the test plates 18 to 25 was measured by conveying to a vessel and measuring the change in thermal conductivity due to hydrogen (inert gas melting-gas chromatograph method).
The contact resistance and the hydrogen concentration in the test plates 18 to 25 (shown as “hydrogen concentration in the test plate” in Table 4) are shown in Table 4 below together with the heat treatment conditions described above. Note that the contact resistance was 0.5 mΩ · cm ² or less, and the hydrogen concentration in the Ti substrate was 70 ppm or less.

Here, the concentration of hydrogen contained in one kind of pure Ti material specified in JIS H 4600 is usually about 20 to 40 ppm.
As shown in Table 4, the test plates 18 and 22 that were not heat-treated under the heat treatment conditions shown in Table 4 had a slightly high contact resistance, and the hydrogen concentration in the test plate was also a high value. That is, good results could not be obtained. Since the hydrogen concentration in the test plate was a high value, it was found that hydrogen was absorbed into the base material of the Ti substrate by exposure to a humidified pure hydrogen atmosphere for 500 hours.
Moreover, as shown in Table 4, the test plates 19 to 21 and 23 to 25 subjected to the heat treatment under the heat treatment conditions shown in Table 4 have low contact resistance, and the hydrogen concentration in the test plate is also low. became. That is, good results could be obtained.

  From the results of <Example E>, the test plates 19 to 21 and 23 to 25 were able to reduce the contact resistance by heat treatment and were exposed to a humidified pure hydrogen atmosphere for 500 hours. It was also confirmed that hydrogen was not absorbed.

<Example F>
Next, in <Example F>, a power generation test was performed in the case of using a separator manufactured using the Ti substrate of the test plate 5 described above.
First, two Ti substrates each having a length of 95.2 mm × width of 95.2 mm × thickness of 19 mm are prepared, and a gas having a groove width of 0.6 mm and a groove depth of 0.5 mm is machined at the center of the surface. The flow path was produced in the shape shown in FIG. Then, a Pd film was formed on the surface of the Ti substrate on which the gas flow path was formed under the same method and conditions as in <Example A>, and a heat treatment was performed to produce a separator.

Then, the produced separator was incorporated into a solid polymer fuel cell (manufactured by Electrochem, fuel cell EFC-05-01SP) as follows, and a power generation test was performed.
First, as shown in FIG. 5, the two separators prepared were placed with the surfaces on which the gas flow paths were formed facing each other, and the carbon cloth was placed on each surface on which the gas flow paths were formed. A fuel cell for power generation test was fabricated by sandwiching a solid polymer film between the carbon cloths.

Hydrogen gas having a purity of 99.999% was used as the fuel gas introduced into the anode electrode side of the fuel cell produced as described above, and air was used as the gas introduced into the cathode electrode side.
The fuel cell is heated and kept at 80 ° C., and the dew point temperature is adjusted to 80 ° C. by passing hydrogen gas and air through heated water, and the fuel cell is operated at a pressure of 2026 hPa (2 atm). Introduced.

Then, using a cell performance measurement system (890CL manufactured by Scribner), the current flowing through the separator was set to 300 mA / cm ² and power was generated for 100 hours to measure the change in voltage.
As a result, the initial voltage of the separator of the Ti substrate of the test plate 5 and the voltage after 100 hours of power generation were both 0.61 V, and no change in voltage was observed.

In addition, as a comparison object, instead of the Ti substrate separator of the test plate 5, a conventionally used graphite separator (manufactured by Electrochem, FC-05MP) is arranged to produce a fuel cell, under the same conditions as above. A power generation test was conducted.
As a result, the voltage at the initial stage of power generation and the voltage after power generation for 100 hours were both 0.61 V, and the result was exactly the same as that of the Ti substrate separator of the test plate 5.

  From the above results, it has been found that the fuel cell separator produced by the method for producing a fuel cell separator of the present invention exhibits the same performance as a graphite separator even though it is a metallic separator.

  The fuel cell separator manufacturing method, the fuel cell separator and the fuel cell according to the present invention have been described in detail with reference to the preferred embodiments and examples. However, the gist of the present invention is limited to the contents described above. The scope of rights should be broadly interpreted based on the claims. Needless to say, the contents of the present invention can be widely modified and changed based on the above description.

It is a flowchart explaining the process of the manufacturing method of the separator for fuel cells which concerns on this invention. (A) And (b) is sectional drawing of the separator for fuel cells which concerns on this invention. It is explanatory drawing explaining the measuring method of contact resistance. It is a figure which shows an example of the shape of the gas flow path formed in the surface of a board | substrate. It is a figure which shows a mode that a part of fuel cell using the separator for fuel cells of this invention was expand | deployed.

Explanation of symbols

S1 Recess formation step S2 Noble metal layer formation step S3 Heat treatment step 1 Fuel cell separator 2 Substrate 3 Noble metal layer 4 Diffusion layer 10 Single cell 11 Gas flow path 12 Gas diffusion layer 13 Solid polymer membrane 20 Fuel cell

Claims (5)

A recess forming step for forming a recess for forming a gas flow path for flowing gas on at least a part of the surface of the substrate as a fuel cell separator made of Ti or Ti alloy;
A noble metal layer having a thickness of 2 nm or more comprising at least one kind of noble metal selected from Ru, Rh, Pd, Os, Ir, Pt and Au is formed on the surface of the substrate on which the concave portion is formed by plasma CVD. A noble metal layer forming step formed by:
A heat treatment step of heat-treating the substrate on which the noble metal layer is formed in the noble metal layer formation step under a predetermined heat treatment temperature and a predetermined oxygen partial pressure;
Including
The predetermined heat treatment temperature in the heat treatment step is 300 to 800 ° C.,
The predetermined oxygen partial pressure in the heat treatment step is
When the noble metal is at least one selected from Ru, Rh, Pd, Os and Ir, 1.33 Pa or less,
In the case where the noble metal is at least one selected from Pt and Au, the oxygen partial pressure at atmospheric pressure or lower is set.   2. The method for manufacturing a fuel cell separator according to claim 1, wherein the noble metal layer forming step forms the noble metal layer by heating the substrate to 300 to 800 ° C. 3. Ru, Rh, Pd, Os, Ir, on the surface of a substrate as a separator for a fuel cell made of Ti or Ti alloy in which a recess for forming a gas flow path for allowing gas to flow through at least a part of the surface is formed. A noble metal layer having a thickness of 2 nm or more containing at least one kind of noble metal selected from Pt and Au is formed by plasma CVD, and the noble metal layer is heat-treated at a predetermined heat treatment temperature and a predetermined oxygen partial pressure. It was obtained by
The predetermined heat treatment temperature is 300 to 800 ° C., and
The predetermined oxygen partial pressure is:
When the noble metal is at least one selected from Ru, Rh, Pd, Os and Ir, 1.33 Pa or less,
When the noble metal is at least one selected from Pt and Au, the fuel cell separator is characterized by having an oxygen partial pressure or less at atmospheric pressure.   The fuel cell separator according to claim 3, wherein the noble metal layer is formed by heating the substrate to 300 to 800 ° C. 5. Fuel cell characterized by using a separator for fuel cell according to claim 3 or claim 4.

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